Microsoft 365 ICS URL Not Working or Not Updating? Here's Why

A Microsoft 365 ICS link that won't import — or imports once and never refreshes again — is one of the most common calendar headaches. Here's what's actually going on.

Common causes

• The feed format is non-standard. Microsoft uses Windows time-zone identifiers and quirks that strict parsers (Google, Apple) reject or misread.
• The publish link was reset. Re-publishing a calendar in Outlook can generate a new URL and silently invalidate the old one.
• The calendar is very large. Some clients struggle with large ICS files and stop refreshing.
• You copied the HTML link, not the ICS link. Outlook offers both — only the one ending in .ics is a subscribable feed.

How to check the link is valid

Paste the URL into your browser. If it downloads a .ics file you can open and see events in, the feed itself works — the problem is how the destination calendar reads it.

The reliable fix

CalConverter re-serves your Microsoft 365 feed as clean, standards-compliant ICS and keeps a refreshed copy, so Google and Apple stop choking on it.

Steps

1. In Outlook on the web, re-publish the calendar (Settings → Calendar → Shared calendars, "Can view all details") and copy the fresh .ics link.
2. Convert it with CalConverter.
3. Subscribe to the converted URL in Google Calendar or Apple Calendar.

If updates ever stop again, the first thing to check is whether the original Outlook publish link is still valid — re-publish and re-convert if not.